Functions of the kidney

1. To excrete waste products of metabolism:

   1. urea, metabolite of protein

   2. uric acid, metabolite of nucleic acid (uric acid, for ex., would be increased in leukemia patients).

2. To regulate concentration of water and electrolytes in our body:

   1. Na+, Cl-, both of which are controlled by our old friend renin-angiotensin system and blood volume

   2. Water, controlled mainly by ADH

   3. K+, regulated by secretion of aldosterone, and by acid/base balance.

   4. Ca2+, PO4(3-), regulated by Vitamin D. (the 1^st hydroxylation of Vit D occurs in the liver (hydroxylation of carbon 1). 2^nd hydroxylation is in the kidney. This hydroxylated vit D from the liver can actually be activated in the kidney (1, 25 colecalciferol) or inactivated in the kidney (24, 25 colecalciferol)

3. To maintain acid/base balance:

   1. secretion of H+

   2. reabsorption of HCO3-

4. Endocrine functions:

   1. production of erythropoietin, which regulates rbc mass. Obviously, with chronic renal failure and decreased production, the person can become anemic.

   2. renin, secreted by juxtaglomerular cells in afferent arteriole, reacts to any changes of blood pressure (or Na concentration)

Category: Nephrology Notes , Physiology Notes